Presentation slide

1. ENVIRONMENTAL MICROBIOLOGY
COURSE CODE: MCB 403
PRESENTATION ON:
SEWAGE TREATMENT AND
DISPOSAL

2. WHAT IS SEWAGE
• Sewage refers to the wastewater that is produced by a community, industrial
processes, or other sources. It typically contains a combination of liquid waste
from toilets, sinks, showers, and other household or commercial activities, as
well as water from storm drains and industrial processes. Sewage may also
contain solid waste, such as toilet paper, food particles, and other debris.
• Sewage is usually carried away from its source through a system of pipes and
drains, known as a sewer system, and transported to a sewage treatment plant.
At the treatment plant, sewage undergoes a series of processes to remove
contaminants, pathogens, and pollutants before the treated water is released
back into the environment, usually into rivers, lakes, or oceans.

3. IMPORTANCE OF PROPER SEWAGE MANAGEMENT
Proper sewage management is of paramount importance for several reasons, ranging from
public health and environmental preservation to economic development. Here are some key reasons
highlighting the significance of effective sewage management:
1.Public Health Protection: Inadequate sewage management can lead to the spread of waterborne
diseases such as cholera, typhoid, and hepatitis. Proper sewage treatment and disposal help prevent
contamination of water sources, reducing the risk of disease transmission and ensuring the well-being
of communities.
2.Environmental Conservation: Untreated sewage released into water bodies can severely harm
aquatic ecosystems. Nutrient-rich sewage can lead to excessive growth of algae, deplete oxygen levels
in water, and disrupt the balance of aquatic life. Proper treatment minimizes these negative impacts and
maintains the health of ecosystems.
3.Water Quality Preservation: Effective sewage management prevents the pollution of freshwater
sources, such as rivers, lakes, and groundwater. Clean water is essential for drinking, agriculture, and
industrial processes, and proper sewage management helps safeguard these resources.
4.Prevention of Contamination: Untreated sewage can contaminate soil, groundwater, and surface
water with harmful pathogens and pollutants. This contamination can have far-reaching consequences
for both human and environmental health. Proper sewage treatment prevents these contaminants from
entering the environment.
5.Tourism and Aesthetics: Clean and aesthetically pleasing environments attract tourism and
recreation, contributing to local economies. Well-maintained sewage systems help maintain a positive
image of an area, benefiting tourism and the overall quality of life for residents.

4. SOURCES OF SEWAGE
Sewage originates from various sources, primarily human
activities and natural processes. It consists of wastewater and waste
materials that are carried away from homes, businesses, and industries.
Some common sources of sewage include:
1.Residential Areas: Wastewater generated from homes, including toilet
flushing, bathing, laundry, and kitchen activities, contributes a significant
amount of sewage.
2.Commercial and Industrial Facilities: Businesses and industries
produce wastewater through processes such as manufacturing, cleaning,
and cooling. This can include chemicals, pollutants, and organic waste.
3.Municipal Infrastructure: Sewage can also come from leaks, overflows,
and breaks in sewage collection and treatment systems, including pipes,
pumps, and treatment plants.
4.Stormwater Runoff: Rainwater and melting snow can pick up pollutants,
debris, and contaminants from streets, roads, parking lots, and other
surfaces as it flows into drainage systems.
5.Agriculture: Agricultural activities like irrigation, pesticide and fertilizer
use, and animal waste can introduce pollutants into water bodies,
contributing to sewage.
6.Septic Systems: In rural or less developed areas, septic systems are
used to treat wastewater from individual households. If not properly
maintained, these systems can contribute to sewage contamination.

6. Sewage Treatment Process
Sewage treatment is the process of removing contaminants and
pollutants from wastewater
1. Preliminary Treatment:
1. Screening: Large objects like sticks, leaves, plastics, and debris are
removed using screens and bar racks.
2. Grit Removal: Sand, gravel, and other heavy particles settle out
through sedimentation or centrifugal action.
2. Primary Treatment:
1. Sedimentation: Wastewater flows into large settling tanks, where
heavier solids (sludge) settle to the bottom as primary sludge, while
lighter materials float to the surface as scum.
2. Primary sludge is removed for further processing, while scum is
skimmed off.
3. Secondary Treatment (Biological Treatment):
1. Activated Sludge Process: Wastewater is mixed with microorganisms
(activated sludge) in aeration tanks. The microorganisms consume
organic matter, breaking it down into carbon dioxide, water, and more
microorganisms.
2. Trickling Filters: Wastewater is sprayed over a bed of rocks or plastic
media coated with biofilm, where aerobic microorganisms remove
organic pollutants.
3. Rotating Biological Contactors (RBCs): A series of rotating disks with
biofilm provide a surface for microorganisms to treat wastewater.
4. Sequencing Batch Reactors (SBRs): Wastewater undergoes
treatment in batches, including aeration, settling, and decanting.
SEWAGE TREATMENT PROCRESS

7. 4. Tertiary Treatment (Advanced Treatment):
1. Tertiary treatment is an additional step used to further purify wastewater when required. It's used
to remove specific contaminants such as nutrients (nitrogen and phosphorus), trace metals, and
residual organic matter.
2. Methods include sand filtration, microfiltration, ultrafiltration, reverse osmosis, and advanced
oxidation processes.
5. Disinfection:
1. Disinfection is the final step to kill or inactivate pathogens before releasing treated water into the
environment or for reuse.
2. Common disinfection methods include chlorination, ultraviolet (UV) disinfection, and ozonation.
6. Sludge Treatment and Disposal:
1. Sludge generated during the treatment process is further treated to reduce its volume and
harmful properties.
2. Treatment methods include anaerobic digestion, aerobic digestion, and mechanical dewatering.
3. The treated sludge may be incinerated, landfilled, used as fertilizer, or disposed of in
accordance with regulations.
7. Effluent Release or Reuse:
1. Treated water (effluent) is released into water bodies like rivers, lakes, or oceans, following
regulatory guidelines.
2. Alternatively, treated water can be further treated for non-potable reuse, such as irrigation,
industrial processes, or even indirect potable water supply.

9. METHOD OF SEWAGE DISPOSAL
Sewage disposal refers to the process of safely and effectively managing and treating wastewater generated from residential, commercial,
and industrial sources. Here are some common methods:
1.Municipal Sewage Treatment Plants: Municipal wastewater treatment plants receive sewage from households, businesses, and industries
through an extensive network of pipes and sewer systems. The sewage undergoes several treatment processes, including primary treatment
(removing large solids), secondary treatment (biological treatment to remove organic matter), and tertiary treatment (additional filtration and
disinfection). Once treated, the water is released into water bodies or reused for non-potable purposes like irrigation.
2.Septic Systems: Septic systems are commonly used in rural or low-density areas where centralized sewage treatment is not feasible. They
consist of a septic tank and a drainfield. Wastewater flows into the septic tank, where solids settle to the bottom and are partially
decomposed. The liquid effluent then moves to the drainfield, where it is further treated by soil and microbial action. Regular maintenance
and proper usage are crucial to prevent system failure.
3.Composting Toilets: Composting toilets are eco-friendly systems that treat human waste through composting and decomposition. They
separate urine from solid waste and use aerobic bacteria to break down the waste into compost over time. The resulting compost can be
safely used as fertilizer for non-food plants.
4.Sewage Lagoons: Sewage lagoons, also known as stabilization ponds, use natural processes to treat sewage. Wastewater is stored in
shallow ponds where sunlight, oxygen, and microorganisms work to break down organic matter. This method is cost-effective but requires
ample space and proper management.

10. 5. Constructed Wetlands: Constructed wetlands mimic natural wetland ecosystems to treat
sewage. Wastewater is channeled through a series of shallow ponds or channels planted with
wetland vegetation. The plants and microbes in the wetlands remove pollutants and nutrients
from the water.
6. Advanced Treatment Technologies: Advanced treatment technologies, such as membrane
bioreactors, activated sludge processes, and advanced oxidation, are employed to further
purify wastewater to higher standards. These methods are often used when stringent water
quality requirements are necessary.
7.On-Site Greywater Treatment: Greywater, which includes wastewater from sinks,
showers, and laundry, can be treated on-site using systems like sand filters, biofilters, and
constructed wetlands. Treated greywater can be reused for irrigation or flushing toilets,
reducing the demand on freshwater resources.